Primary structural studies on bovine platelet factor 4 (PF 4) are in progress. Intact, chemically modified human PF 4 and its bacterial protease, chymotryptic, and tryptic peptides are being used as ligands in affinity chromatographic procedures to evaluate the heparin binding properties of the molecule and its fragments. Characterization of the resultant heparin fractions as to anticoagulant activity, size, charge, and composition is planned. Human placental thromboplastin (TPLN) is being isolated, characterized and compared to bovine brain and lung isolates. Isolation of the protein components will be by established methods using ethanol extraction of phospholipids followed by protein solubilization in carbonate buffered deoxycholate solution and gel filtration. Further purification of the isolate and those obtained from brain and lung tissues will be attempted using DEAE and affinity chromatography procedures with deoxycholate as a ligand.